This research is designed to study the effect of 81 mg and 325 mg of aspirin (ASA) on the individual abilities of enalapril and losartan to lower blood pressure. A secondary objective is to characterize any observed interaction between ASA and losartan or ASA and enalapril by measuring urinary prostanoid concentrations. The null hypothesis is that there is no difference in blood pressure when a low dose or average dose of ASA is added to a monotherapy regimen of either enalapril or losartan. A total of 18 subjects will be recruited, 9 each taking enalapril or losartan. The study involvesa 3, 2 week treatment periods with either ASA 81 mg, ASA 324 mg or placebo each separated by 2 week washout periods. Sitting BP will be collected via cuff manometry and 12-hour urine collections will be completed and analyzed for PGE2, PGE-M, 6-keto- PGF1alpha, 2,3 dinor-PGI-M, TXB2 and TX-M. Plasma norepinephrine concentrations will also be collected. Urine and plasma analyses and comparisons will only be performed if there is a statistical difference observed in blood pressure between the placebo and ASA-treatment periods.